104: BOTRYDIUM GRANULATDM. 



are thin transparent membranes only, without any cellular struc- 

 ture, and when the plant is alive they remain distended to their 

 very utmost from the pressure of the fluid within. The young 

 vesicle which, as will be observed, is -only the swollen apex of 

 a branch of the creeping or underground stem, when it emerges 

 from the ground it is frequently only a clear transparent sac 

 filled almost to bursting with a watery fluid ; after a time minute 

 green spherical grains will be seen, mostly adhering in little 

 groups to each other, and at length they take up their position on 

 the wall of the inner membrane, until the whole vesicle appears 

 to be filled with them ; but the vesicle being filled with them is 

 only in appearance, as it is only the walls that are covered, 

 with a few exceptions of granules floating in the fluid. When a 

 full-grown plant is pressed between slips of glass and examined 

 the membranes composing the vesicle will be seen to shrink up into 

 folds, on which are seen the adhering granules. When the plants 

 are full-grown the epidermis is furfuraceous, or having a number 

 of minute scale-like processes attached to it, as if it were a very 

 thin outer membrane broken up. 



These vesicles have generally been treated as separate and 

 distinct plants, but it will be observed by the sketch, and also 

 Dilwyn has shown, that several of these vesicles are attached to 

 underground stems, and I find, as it has been before observed, that 

 the vesicles are only the apices of the young branches of under- 

 ground stems. These, then, it will be observed, are all attached, 

 forming a kind of system, the tubular stems connecting all the 

 vesicles together, so that we have a minute spreading underground 

 plant whose branches rise to the surface, where they swell into little 

 ovate or spherical vesicles. Now Dilwyn has made his plant sep- 

 tate, or in other words, has divided the connecting tubes or stems 

 by little nodes or rather diaphragms, consequently cutting off the 

 communication between the different parts of the plants, so that it 

 would be impossible for the granulose matter to traverse the 

 tubes, except in the internodes. In my examination of groups 

 of this plant, after having washed the stems perfectly clean, I could 

 only detect one septum, and the tubes appeared to me perfectly free, 

 and that the granulose matter can float freely in them. I noticed 

 particularly that the full-grown plants contained the largest grains, 

 with a large proportion also of minute granules, the larger 

 generally having several of the minute ones attached to them. This 

 led me to investigate them still further, and I now feel convinced 

 in my own mind that the small granules are zoospores, which attach 

 themselves to the larger or female grains, for on liberating some 

 of these on a slip of glass and examining them carefully under the 

 microscope, I distinctly saw the minute granules moving about as 

 I have seen zoospores in fresh-water Algas. 



Finding some of the vesicles of apparently the same age as 

 others containing only minute granules, whilst others contained both 



